1. Field of the Invention
This invention relates to signal processing apparatus and particularly to a circuit for processing digital signal data from signal sources such as sensors in a radar system.
2. Description of the Prior Art
In systems in which a relatively small number of signal sources generate a large amount of high speed data, such as in radar systems, adaptive signal tracking and excision is often used. In such systems, sensors monitor an external environment and report parameter packets, each parameter packet containing data related to each event that is detected from any of these signal sources. Thus, for example, the signal sources can be scanned and data received therefrom packetized for transmission to a processor. The data within these parameter packets represent a set of uniquely different measurements of the signal, for example, frequency, amplitude, etc.
If it is expected that the measured parameters for any particular signal source do not rapidly change in time, and are significantly different from parameters measured from other sources, the signal from a selected signal source can be filtered on the basis of the values of the detected parameters.
The filtering process, in general, involves testing each of the parameters in a packet against a predetermined set of corresponding data. Each set of data can be considered as a window. If the value of each tested parameter falls within the window, then the packet matches the filter criteria. There can be several sets of filter criteria, and hence all sets must be sequentially tested.
Upon finding a filter match, two actions can result: "excision", which means that upon a match, that parameter packet is discarded from the data flow, or "track", which results in the transfer of the parameter data to a follow on processor.
If the filtered data signal is input to a signal processor, the processor can set up the filter criteria based on some sort of adaptive criteria. The adaptive criteria algorithms usually attempt to sort the packets into uniquely different signal tracks and after a sufficient number of packets are received for a particular track, the filter is given an excision parameter set. Adaptive excision, in this context, minimizes the data flow to the processor, since it tends to be responsive to only new signal sources.
A similar approach can be used to track signals, where the processor can direct the filter to pass packets which fit a given set of parameters and reject all others.
However in such systems, the existing window criteria must be sequentially compared to the corresponding signal parameters. For a large number of stored filtered parameter sets, the maximum input data rate is limited by the speed at which the hardware can perform that number of sequential comparisons.
It is possible to eliminate the sequential parts of the process if all comparisons are performed in parallel. However this would require a larger number of data registers and associated comparators if the number of parameter sets is large.